Alexander technique teachers refer at times to faulty sensory appreciation, unreliable sensory appreciation, or debauched kinesthesia to explain why a student may feel like they are doing one thing when in fact they are doing another. For example, a student who habitually tilts their neck to the left may feel like their neck is vertical even though a look in the mirror shows otherwise. These terms originated with F.M. Alexander, the founder of the Alexander technique. Few modern neuroscientists would use the word “faulty” (much less “debauched”) in this context, and “reliability” has a specific scientific definition that is not what is meant here1In a scientific context, reliability refers to whether a measurement device gives you the same result every time, not whether that result is correct (accurate) or fine-grained (precise).. However, it is well-established that our ability to perceive the world “veridically” (as it really exists) is subject to inherent limitations at multiple levels of the nervous system.

Sensation vs. perception

To understand how this works, it is important to know that scientific literature makes a key distinction between sensation and perception. This is completely standard; most university catalogs will include a class called “sensation and perception” in their “biological bases of behavior” offerings for psychology or neuroscience majors. Sensation is the raw signal as detected by the sensory organs – mainly, the eyes, ears (including the vestibular organs in the inner ear), nose, tongue, skin, and proprioceptors2Proprioceptors include position sensors, velocity sensors, and force receptors embedded in the muscles, tendons, and joints.. Perception is the experience of vision, hearing, balance, smelling, tasting, touching, and kinesthesia (body position and movement).

The main reason that perception is not the same as sensation is that raw sensory information entering the nervous system is noisy (think of a radio station with a lot of static) and incomplete, and the brain invests a lot of processing power to make sense of the information. Perception therefore relies on both incoming sensory data and extensive interpretation. The stream of information coming from the sensory organs toward awareness is called “bottom up” processing, and the influence of information from memory, context, expectations, and so on is called “top down” processing. Both are essential, and both are inherently flawed.

Another important distinction between sensation and perception is that perception is multisensory. It is tempting to think that you could draw a simple diagram with a line from each sensory organ to its respective perception, but the reality is more complex and interesting (de Gelder, 2003). For instance, our sense of balance relies on vision and proprioception as well as the vestibular organs (Horak, 2006), our sense of taste relies on information from the nose and throat as well as the tongue (Dalton 2000), and what we hear is influenced by what we see (McGurk, 1976). (Check out this video of the McGurk Effect for a fascinating example of this phenomenon.)

Top down influence in the visual system

Although the distinction between sensation and perception applies to all the senses, the majority of research has been conducted on the visual system, and a good way to get a feeling for the difference between sensation and perception is to look at visual illusions. These are stimuli that have been purposely designed to take advantage of known biases in the visual system. Biases arise because extensive experience in the real world tells us that certain sensory input usually mean certain things. Illusions uncover these biases by providing an unusual context. For instance, in this illusion, you may find it hard to believe that the two squares with arrows pointing to them are the same color (Shenoy, 2011). I always have to prove it to myself by poking two holes in a piece of paper and covering the picture so that only those two squares are visible. (Go ahead and do that. I’ll wait.) This illusion is so powerful because it takes advantage of the perceptual system’s ability to automatically compensate for differences in shading. We “know” that the lower left face of the cube is in the shade, while the top face is in the light. And for most purposes, this is correct! So the mismatch between the “true” color and what we perceive is actually adaptive and useful, and it only becomes “wrong” in the context of an illusion like this (or when you are trying to mix paints).

Another benefit of top-down processing is that it allows us to fill in missing information. For instance, if you have never seen this picture before, it may take you a while to see the dog in it – but once you have perceived the dog, it becomes easy to spot (Wallisch, 2017).

The take-home message here is that raw, incoming sensory information is never perfect. In fact it is messy, noisy, blurry, incomplete, and tangled up with unrelated information. Top-down processing is essential to make sense of it all. However, top-down processing is also imperfect, as it relies on our previous experience, expectations, and beliefs.

Top-down influence in the kinesthetic system

I’ve provided examples of top-down processing in visual perception, but what about kinesthetic perception? The main source of top-down information for kinesthesia is our stored set of understandings about how our own body is configured. This set of knowledge, known as body schema, includes our underlying (mostly unconscious) understandings of where our joints are located and in what directions (and how far) they bend; how long our limbs are; how much physical volume we occupy; how far we can reach without falling down, and so on. [Note that body schema is at least theoretically distinct from “body image,” which is a set of conscious thoughts about one’s body (pretty, ugly, fat, skinny, muscular, etc.)] The sensory information received from our muscles, joints, skin, and eyes is interpreted in the context of our body schema to produce a coherent perceptual experience, and to plan and generate movements.

Body schema is built from experience (Assaiante, 2014). Infants flail in every direction and eventually figure out what is where. Older children and adults continue to refine our sensitivity to, and understanding of, positions that are deemed useful (such as those needed for bringing food to the mouth), while ignoring, and thus reducing sensitivity to, positions not deemed useful. These adaptations occur because the brain is “plastic” (Kleim, 2008). It changes in response to its own pattern of activity, growing new neurons and new synapses to support exploration and consolidate habits, while allowing unused pathways to languish and die. The good news is, even a small amount of practicing something new can cause the growth of new neurons and connections to support the new activity (Ilg, 2008).

Like vision, kinesthesia is susceptible to illusion. For instance, applying a vibration to your muscle sends a signal to the muscle spindle that the muscle is lengthening, which can lead to interesting effects. If you have a smartphone (or other vibrating device), you can investigate this for yourself. First, find an app that will make the phone vibrate constantly. Then close your eyes and touch the phone to your gently flexed bicep. Most people will experience the feeling of the elbow straightening; when you open your eyes, you will see a mismatch between the actual arm position and how it felt. If you have a friend handy, you can explore this further. Have your friend stand with eyes closed, and apply the vibration to their Achilles tendon. They will feel like they are falling forward, and you may see them sway visibly as they try to reconcile the different sources of information they are receiving.

In the examples above, interference was applied to the the raw data (sensation) coming in. Another fascinating kinesthetic illusion relies on the multisensory top-down nature of perception. This is the famous “rubber hand illusion.” To try this, you will need a partner.

The person in the “subject” role sits at a desk. Put a large hardcover book on the subject’s lap and have them rest their hand on the book, palm down. It is crucial that they cannot see their hand, but that you can reach it.

Put a fake hand on top of the desk, directly over where the subject’s real hand is, and oriented in exactly the same direction. The two hands should match (e.g., if the hand under the desk is a right hand, the hand on top of the desk should also be a right hand.) If there is another person present with similar sized hands, you can use their hand as the fake hand on top of the desk. Alternatively, you can use an inflated rubber glove.

Using both of your hands, gently brush the two hands in exactly the same way at exactly the same time. If you have two matching paint brushes, you can use one in each hand. Repeat the simultaneous brushing for a minute or so while the subject looks at the hand on top of the desk. You can also include gentle tapping.

After a while, the subject may start to feel like the hand on top of the desk is their own. This illusion illustrates how quickly the body schema can adapt to incorporate new (and strange) information.

In the above video, Patrick Johnson demonstrates the “rubber hand illusion” when you don’t have a rubber hand.

Improving kinesthesia

Scientific understanding of the importance of an accurate body schema for healthy posture and movement is growing. For instance, Parkinson’s disease, which is best known for its motor symptoms (tremor, slow and small movements, balance deficits, and stooped posture) is also marked by deficits in both proprioception and body schema (Cohen, 2011). In addition, kinesthetic deficits have been found in people with chronic back pain (Bray 2011), who also tend to have altered movement patterns (Scholtes, 2009). Early evidence suggests that neck pain, too, may be associated with changes in body schema.

The adaptability of the body schema means that it is susceptible to unhealthy influences. It also means that interventions designed to improve the accuracy of the body schema (one of several common elements of a typical Alexander technique lesson) hold promise. From the established science above, we can reasonably hypothesize, for instance, that practicing moving at your hip joints (rather than bending at your “waist”) is likely to modify your brain’s representation of how your body is put together. In addition, studies of people with anorexia have indicated that the conscious and unconscious representations of our body are not completely distinct (Spitoni, 2015). Applying this insight to the previous example, we might hypothesize that simply becoming aware of where your hip joints are located may influence the body schema, which can in turn change how you move. These specific ideas have not yet been tested, but they are not a great leap from what has already been shown, and they are testable.

Refinements to bottom-up processing are also possible. This can be observed as changes in the primary somatosensory cortex of the brain. The somatosensory cortex is organized so that adjacent areas of the brain are associated with adjacent areas of the body, and body parts with more tactile sensitivity (e.g. fingertips) have more associated cortical volume than body parts with less tactile sensitivity (e.g. shins). Because the brain is “plastic,” these volumes can grow and shrink depending on use and attention. For example, the volume of sensory cortex associated with the finger expands if that finger is used to read Braille. Sensory cortex is also different in people with dystonia and in people with chronic pain. There is room for more scientific exploration on how to stimulate advantageous neuroplasticity here.

In sum, debauched kinesthesia and faulty sensory appreciation are outdated terms that refer to scientific concepts that are highly relevant. Alexander teachers would be better able to communicate with medical professionals and other scientifically literate people if we updated our language. Perception of body position and movement (kinesthesia) is affected by noisy “bottom-up” information from sensory organs, by multisensory information, and by “top-down” information from the cerebral cortex (body schema). The Alexander technique is likely to affect the body schema along with other crucial cognitive and neural functions, and thereby to affect movement planning and generation. The idea that correcting body schema deficits could improve movement is reasonable and should be readily testable in an experimental situation.

Acknowledgements

I would like to thank Andrew McCann and Patrick Johnson for helpful comments on earlier drafts.

Scholtes SA, Gombatto SP, Van Dillen LR. Differences in lumbopelvic motion between people with and people without low back pain during two lower limb movement tests. Clin Biomech. 2009;24(1):7–12. doi:10.1016/j.clinbiomech.2008.09.008.